The present invention relates to a massaging device for insertion in the back of massage chairs or the like.
Conventional massaging devices for insertion in the back of massage chairs or the like generally comprise a frame which supports, so that they can rotate about their respective axes, an upper shaft and a lower shaft which are arranged so that their axes are parallel and substantially horizontal. The upper shaft and the lower shaft have, at their two opposite longitudinal ends, eccentric portions having a circular cross-section and which can be likened to cranks, each portion rotatably engaging an arm which supports, at its opposite end, a wheel which can rotate freely about its own axis, which is usually slightly inclined with respect to a horizontal direction which is parallel to the axes of the upper and of the lower shafts.
Each one of the arms is pivoted, proximate to one of its intermediate portions, to an eccentric portion of the lower shaft which can also be likened to a crank.
Each one of the arms is connected to the eccentric portion of the lower shaft by a linkage. The linkage is articulated in an intermediate point so as to allow to vary its useful length and connect it to the corresponding eccentric portion of the lower shaft by means of a spherical joint.
The axis of the eccentric portions of the upper shaft which engage the arms is slightly inclined with respect to the axis of the upper shaft. As a consequence of the geometry of the eccentric portions, the rotary actuation of the upper and of the lower shafts causes an oscillation of the wheels, which constitute the parts of the massaging device that act on the back of the user, about a respective axis which passes through the point where the axis of the corresponding eccentric portion of the upper shaft intersects the corresponding axis of the upper shaft; in other words, a movement in a horizontal direction occurs, thus producing the massage known as "stretching", and a vertical movement, producing the massage known as "tapping".
The rotary actuation of the upper and of the lower shafts about their respective axes is achieved by means of a single motor which, by means of a belt drive, turns a transmission shaft arranged transversely to the upper and to the lower shafts and connected thereto by means of two pairs of helical gears. The helical gears arranged on the transmission shaft are connected to the transmission shaft by unidirectional bearings, i.e., bearings which can only rotate in one direction, allowing the corresponding gear to rotate freely with respect to the transmission shaft, and which lock in the opposite direction, rigidly rotationally coupling the corresponding gear to the transmission shaft.
The bearing of one of the gears arranged on the transmission shaft rotates freely in one direction, whilst the bearing of the other gear arranged on the transmission shaft rotates freely in the opposite direction.
In this manner, by means of a single motor which is actuated once in one direction and once in the other direction, the upper and lower shafts are rotated alternatively, the upper shaft producing the oscillating motion of the massage wheels, i.e., their movement in a substantially horizontal direction, the lower shaft moving the massage wheels substantially in a vertical direction.
This device has the drawback of being very noisy during operation.
Moreover, as a consequence of the alternating actuation of the upper and of the lower shafts, i.e., of a nonsimultaneous actuation of the two shafts, the two stretching and tapping massage functions are performed separately.